The present invention generally relates to wireless communications, and more specifically to a wireless portable telephone that selects a single voice service option from among a plurality of voice service options supported by the portable phone.
Wireless portable and mobile telephones have become commonplace as an accepted addition to or replacement for conventional landline telephone systems. Wireless portable or mobile telephones offer the convenience of wireless communications from almost any location in the country or the world.
Wireless telephones, which include both satellite and cellular phones, are communications devices that function in a wireless environment. There are three basic types of wireless telephones. Portable phones are typically small, handheld devices that can be carried on the person. Mobile phones are typically mounted in a vehicle; they have a base unit or cradle that is fixedly mounted to the vehicle, usually inside the passenger compartment, and a handset that is connected to the base unit or cradle by a wire. A fixed wireless phone is usually mounted in a single location. Any of these types of phones can be operated over a terrestrial cellular network or over a satellite communications network. Some wireless phones are capable of operating over both cellular and satellite systems.
Wired phones are those connected directly to a wireline phone system by wires. Wired phones are the typical standard phones found in what is called POTS (Plain Old Telephone Systems). Telephones that operate over short range wireless links, such as portable phones that are used in the home or small business environment, and which transmit to and receive signals from a single fixed base station or unit over a short range (for example, several hundred to a thousand meters), where the base unit is directly connected to a wireline communications network, are not considered wireless phones for purposes of this disclosure. Such single station, short range wireless phones are called xe2x80x9ccordless phonesxe2x80x9d and are considered to fall in the category of standard wireline phones (that is, phones connected to the communications network by wires).
In any given geographic region there may be a number of wireless telephone service providers, each operating their own wireless telephone network, which may cover an entire country or just a region. Each wireless telephone service provider may support different voice service options. For example, in a code division multiple access (CDMA) cellular telephone network, the voice service options can include an IS-96-A voice service option (hereafter xe2x80x9c8K voice service optionxe2x80x9d), an IS-733 voice service option (hereafter xe2x80x9c13K voice service optionxe2x80x9d), and an IS-127 voice service option (hereafter xe2x80x9cEVRC voice service optionxe2x80x9d). Each of the foregoing IS specifications is available from the Telecommunication Industry Association (2001 Pennsylvania Avenue, Suite 800, Washington, DC 20006). Today, the EVRC voice service option is the preferred voice service option because of its high quality and low bandwidth.
Problems arise when not all of the service providers support the same voice service options. For example, if service provider Y offers the EVRC voice service option, but service provider X does not, then when a customer of Y travels into X""s region, the customer may not be able to make or receive phone calls. This will be the case when the customer""s wireless phone is configured for the EVRC voice service option and X""s network does not support voice service option negotiation.
What is desired, therefore, is a subscriber unit that supports multiple voice service options and can intelligently select a voice service option when originating and receiving a call.
The present invention provides a system and method for selecting a voice service option for a wireless communication device.
In one aspect, the invention provides a subscriber unit that supports more than one voice service option and selects the appropriate voice service option when originating and receiving a call. The subscriber unit includes a memory to store parameter values, including a first voice service option parameter value and a second voice service option parameter value. The subscriber unit also includes a means for determining whether the subscriber unit is within a home system or is roaming, and a selecting means for selecting a voice service option from among at least a first voice service option corresponding to the first voice service option parameter value and a second voice service option corresponding to the second voice service option parameter value. The selecting means selects the first voice service option if the subscriber unit is within the home system, and selects the second voice service option if the subscriber is roaming. Typically, the first voice service option is different from the second voice service option.
Advantageously, the selecting means includes means for creating a call request message, wherein the call request message includes a voice service option field for storing a voice service option value, means for placing the first voice service option parameter value in the voice service option field when the subscriber unit is in a home system, means for placing the second voice service option parameter value in the voice service option field when the subscriber unit is roaming, and means for transmitting the call request message.
Preferably, a third voice service option parameter value is also stored in the non-volatile memory. Additionally, the selecting means also includes means for creating a page response message, wherein the page response message includes a voice service option field for storing a voice service option value, means for placing the third voice service option parameter value in the voice service option field when the subscriber unit is in a home system, and means for transmitting the page response message.
In another aspect, the invention provides a method for a subscriber unit to select a voice service option when originating a call, where the subscriber unit includes a memory that stores a first voice service option value and a second voice service option value. In one embodiment, the method includes the steps of determining whether the subscriber unit is in a home system, and if the subscriber unit is in a home system, retrieving from the memory the first voice service option value. But, if the subscriber unit is not in a home system, the method includes the step of retrieving from the memory the second voice service option value. The method also includes the steps of creating a call request message having a voice service option field, storing in the voice service option field the voice service option value retrieved from the non-volatile memory, and transmitting the call request message to initiate the call.
Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with reference to the accompanying drawings.